System and method for diffuser aft plate assembly

ABSTRACT

A method includes inserting axially a radially interior surface of an aft plate assembly into a circumferential groove of an inner barrel of a diffuser section of a gas turbine, where the aft plate assembly is inserted into a first circumferential orientation relative to the circumferential groove, and the circumferential groove is disposed on a radially exterior surface of the inner barrel. The method includes rotating the aft plate assembly circumferentially within the circumferential groove from the first circumferential orientation to a second circumferential orientation, where the inner barrel is configured to axially retain the aft plate assembly when the aft plate assembly is disposed in the second circumferential orientation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation in Part of U.S. patent applicationSer. No. 14/951,090, entitled “SYSTEM AND METHOD FOR TURBINE DIFFUSER,”filed Nov. 24, 2015, U.S. patent application Ser. No. 14/951,151,entitled “SYSTEM OF SUPPORTING TURBINE DIFFUSER,” filed Nov. 24, 2015,U.S. patent application Ser. No. 14/951,164, entitled “SYSTEM OFSUPPORTING TURBINE DIFFUSER OUTLET,” filed Nov. 24, 2015, and U.S.patent application Ser. No. 14/951,173, entitled “SYSTEM OF SUPPORTINGTURBINE DIFFUSER,” filed Nov. 24, 2015, which are herein incorporated byreference in their entirety.

BACKGROUND

The subject matter disclosed herein relates to gas turbine engines, suchas an improved diffuser section.

Gas turbine systems generally include a compressor, a combustor, and aturbine. The compressor compresses air from an air intake, andsubsequently directs the compressed air to the combustor. The combustorcombusts a mixture of compressed air and fuel to produce hot combustiongases directed to the turbine to produce work, such as to drive anelectrical generator.

Traditional diffuser sections of the turbine are subject to highstresses due to the configuration of the diffuser section and hightemperatures associated with the exhaust gases. Accordingly, traditionaldiffuser sections experience high stresses, thereby increasing the wearon the diffuser section.

BRIEF DESCRIPTION

In one embodiment, a method includes inserting axially a radiallyinterior surface of an aft plate assembly into a circumferential grooveof an inner barrel of a diffuser section of a gas turbine, where the aftplate assembly is inserted into a first circumferential orientationrelative to the circumferential groove, and the circumferential grooveis disposed on a radially exterior surface of the inner barrel. Themethod includes rotating the aft plate assembly circumferentially withinthe circumferential groove from the first circumferential orientation toa second circumferential orientation, where the inner barrel isconfigured to axially retain the aft plate assembly when the aft plateassembly is disposed in the second circumferential orientation.

In one embodiment, a system includes a diffuser section configured toreceive an exhaust gas from a turbine section, where the diffusersection includes an aft plate assembly comprising a radially interiorsurface, where the radially interior surface comprises a first notch anda first ridge. The diffuser section comprises an inner barrel includinga circumferential groove disposed on a radially exterior surface, wherethe circumferential groove includes an upstream lip and a downstream lipcomprising a second notch and a second ridge. The first ridge isconfigured to be disposed in the circumferential groove when the aftplate assembly is disposed in a first circumferential orientation and asecond circumferential orientation relative to the inner barrel, thefirst ridge is axially aligned with the second notch in the firstcircumferential orientation, and the first ridge is circumferentiallyoffset from the second notch in the second circumferential orientation.

In one embodiment, a system includes a diffuser section configured toreceive an exhaust gas from a turbine section, where the diffusersection includes a forward plate, and an aft plate assembly comprising aradially interior surface, where the radially interior surface comprisesa first plurality of notches and a first plurality of ridges. Thediffuser section includes an inner barrel including a circumferentialgroove disposed on a radially exterior surface, where thecircumferential groove includes an upstream lip, and a downstream lipincluding a second plurality of notches and a second plurality ofridges. The diffuser section includes a plurality of poles coupledbetween the forward plate and the aft plate assembly when the aft plateassembly is disposed in a second circumferential configuration relativeto the inner barrel, where the first plurality of ridges is configuredto be disposed in the circumferential groove when the aft plate assemblyis disposed in a first circumferential orientation and the secondcircumferential orientation relative to the inner barrel, the firstplurality of ridges is axially aligned with the second plurality ofnotches in the first circumferential orientation, and the firstplurality of ridges is circumferentially offset from the secondplurality of notches in the second circumferential orientation.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a block diagram of an embodiment of a turbine system having aturbine that includes a modified diffuser section;

FIG. 2 is a detailed diagram of the diffuser section of the turbinedisposed within an exhaust plenum;

FIG. 3 depicts the modified upper portion of the diffuser;

FIG. 4 depicts a cross-sectional view of the diffuser taken through thebrackets along line 4-4 of FIG. 2;

FIG. 5 depicts a perspective view of the lap joint and the discretebracket, along line 5-5 of FIG. 4;

FIG. 6 depicts a perspective view of the lap joint and the discretebracket, along line 5-5 of FIG. 4;

FIG. 7 depicts an axial cross-sectional view of the circumferentialgroove within the inner barrel of the diffuser of FIGS. 2 and 3;

FIG. 8 depicts an axial view of an embodiment of the aft plate assemblytaken along line 8-8 of the diffuser of FIG. 7;

FIG. 9 depicts a partial cross-sectional view of the aft plate assembly;

FIG. 10 depicts an axial view of an embodiment of the aft plate of theinner barrel taken along line 8-8 of the diffuser of FIG. 7;

FIG. 11 depicts an axial view of an embodiment of the aft plate assemblyof the inner barrel taken along line 8-8 of the diffuser of FIG. 7;

FIG. 12 describes a method of forming the aft plates segments accordingto an embodiment of the present disclosure;

FIG. 13 depicts a side view of an embodiment of the outer barrel;

FIG. 14 depicts a side view of the inner barrel;

FIG. 15 illustrates exemplary equipment used to machine the inner barreland the outer barrel into the desired continuous curvature, as describedin FIGS. 13 and 14; and

FIG. 16 illustrates a method of forming the inner barrel and the outerbarrel by the spinning process.

DETAILED DESCRIPTION

A system and methods for improving traditional diffuser sections throughutilization of mechanical improvements on the diffuser section isdescribed in detail below. The mechanical improvements to the diffusersection contribute to improved mechanical integrity of the diffuser byreducing stresses associated with a traditional diffuser design. Themechanical improvements to the diffuser include an aft plate assemblywith notches and ridges to facilitate axial installation of the aftplate to an inner barrel. The aft plate may be inserted axially throughnotches of a circumferential groove of the inner barrel of the diffusersection, then rotated circumferentially within the circumferentialgroove such that ridges of the aft plate axially retain the aft plateassembly. Other mechanical improvements include manufacturing a desiredcurvature of the diffuser section, disposing a plurality of polesbetween a forward plate and the aft plate of the diffuser, acircumferential groove disposed in the inner barrel to receive the aftplate, a circumferential lap joint of the outer barrel, a plurality ofdiscrete brackets disposed along the inner barrel and/or the outerbarrel of the diffuser configured to couple the diffuser to the turbineoutlet, or any combination thereof. The curvature of the diffusersection is implemented by a machine process, such as a spinning process.The spinning process involves molding a suitable material (e.g.,stainless steel, metal) for the inner barrel and the outer barrel intothe desired shape (e.g., curved) by placing the material over a mold.The material is then molded into the desired shape by utilizing a rollerto press the material into the mold, thereby gradually forming thedesired mold shape. To reduce any residual stresses encountered via thespinning process, the inner and outer barrels may be formed from variousaxial segments (e.g., first plurality of axial segments, secondplurality of axial segments). Utilizing axial segments to create theinner barrel and the outer barrel may require less deformation of thematerial to create the desired shape of the inner barrel and the outerbarrel, thereby contributing to reducing the amount of residual stressesthat occur.

Once the axial segments (e.g., first plurality of axial segments, secondplurality of axial segments) of the inner barrel and the outer barrelare formed, the axial segments of each respective barrel may be joinedtogether. The axial segments may be cut to ensure the axial segments(e.g., first plurality of axial segments, second plurality of axialsegments) have excess material so that the segments can be adequatelyjoined together. The axial segments by be joined together by welding,brazing, fusing, bolting, fastening, or any combination thereof.

The poles are disposed between the inner barrel and the outer barrel,which are in turn disposed around the turbine axis. The poles serve tocouple the downstream end of the aft plate to the downstream end of theforward plate via the plurality of poles and are circumferentiallyspaced about the turbine axis. In some embodiments, the poles havevarying pole diameters. The pole diameter is based in part on thecircumferential location of the pole location along the diffuser (e.g.,the outer aft plate, the inner aft plate). For example, the diameter ofthe poles nearest a top portion of the diffuser (e.g., the outer aftplate, the inner aft plate) may have a larger diameter than the polesnearest a bottom portion of the diffuser. In some embodiments, the polediameters are smaller due to their proximity to flow of the exhaustgases. As such, smaller pole diameters may be beneficial by reducingblockage of the exhaust flow path due to the smaller diameters. Thepoles disposed within the top portion of the diffuser section may beconfigured to support the load (e.g., weight) of the diffuser section,such as during installation. For example, the poles disposed within thetop portion of the diffuser section may be utilized to lift the diffusersection. In some embodiments, the poles disposed within the top portionof the diffuser section may be coupled to a hoist, lift, crane, or othersuitable lifting machine to translate the diffuser section to a suitablelocation (e.g., translation for installation, removal, service, repair).The poles may reduce vibration between the inner barrel and the outerbarrel. The arrangement of the poles depends in part on the diameters ofthe poles. The poles nearest the top portion of the diffuser have largerdiameter to bypass vortex shedding frequencies where the velocity of theexhaust gases is more uniform.

The circumferential groove is located at an end of the inner barrel. Theaft plate may be inserted into the circumferential groove, such that theaft plate interfaces with portions of the root of the circumferentialgroove. The circumferential groove may reduce stress by enabling the aftplate to move within the circumferential groove. The hoop stresses maybe reduced in the region by enabling slight movement between thesections (e.g., the aft plate and the circumferential groove). Thestress reduction from implementing the circumferential groove may reducehoop stresses by as much as one-half relative to a diffuser without thecircumferential groove. In some embodiments, the aft plate may be formedas an aft plate assembly. For example, the aft plate assembly mayinclude a plurality of aft plate segments arranged to form an annularaft plate assembly. The aft plate assembly may include a plurality ofnotches and ridges. The aft plate segments may enable some leakage ofthe exhaust gases through openings (e.g., the ridges) into the exhaustplenum. This leakage may reduce the amount of thermal stresses in thearea by enabling a controlled leakage of the hot exhaust gases to passthrough the openings. The aft plate assembly may be inserted axiallyinto a first circumferential orientation relative to the circumferentialgroove. The aft plate assembly may rotate circumferentially within thecircumferential groove from the first circumferential orientation to asecond circumferential orientation. The inner barrel may be configuredwith the ridges and notches to axially retain the aft plate assemblywhen the aft plate assembly is disposed in the second circumferentialorientation.

The circumferential lap joint is disposed between the downstream end ofthe outer wall of the turbine outlet and the upstream end of the outerbarrel of the diffuser section. The circumferential lap joint isconfigured to facilitate axial movement of the outer barrel relative tothe outer wall, thereby relieving stress in the outer barrel. Anupstream lip (e.g., outer lip) of the outer barrel may be disposedradially within a downstream lip (e.g., lip) of the outer wall tofacilitate ease of axial movement of the lap joint. The stress reductionby use of the upstream lip and the downstream lip of the circumferentiallap join may be further increased by the use of discrete brackets. Thediscrete brackets may be coupled to the outer barrel and a frameassembly (e.g., exhaust frame). The discrete brackets (e.g., outerbarrel discrete brackets) are configured to support the outer barrel inthe axial direction. A subset of the discrete brackets (e.g., discreteinner brackets) may be disposed circumferentially around the innerbarrel of the diffuser. The discrete inner brackets (e.g., the innerbarrel support brackets) may hold the diffuser (e.g., inner barrel) inplace and reduce movement in the axial direction. The movement of thediffuser (e.g., the inner barrel and the outer barrel) relative to theturbine outlet may be reduced and/or restrained depending on where thelap joint and discrete bracket are disposed along the outer barrel.

Turning now to the drawings and referring first to FIG. 1, a blockdiagram of an embodiment of a gas turbine system 10 is illustrated. Thediagram includes a fuel nozzle 12, fuel 14, and a combustor 16. Asdepicted, fuel 14 (e.g., a liquid fuel and/or gas fuel, such as naturalgas) is routed to the turbine system 10 through the fuel nozzle 12 intothe combustor 16. The combustor 16 ignites and combusts the air-fuelmixture 34, and then passes hot pressurized exhaust gas 36 into aturbine 18. The exhaust gas 36 passes through turbine blades of aturbine rotor in the turbine 18, thereby driving the turbine 18 torotate about the shaft 28. In an embodiment, a modified diffuser 38 iscoupled to the turbine 18. The turbine 18 is coupled to a turbineoutlet, where the turbine outlet and the diffuser 38 are configured toreceive the exhaust gases 36 from the turbine 18 during operation. Asdiscussed in detail below, embodiments of a turbine system 10 includecertain structures and components within the diffuser 38 that improvethe reliability associated with manufacturing the diffuser 38 (e.g., byreducing stress). Embodiments of the turbine system 10 may includecertain structures and components of the diffuser 38 to improve theproduction time of the diffuser 38. The exhaust gas 36 of the combustionprocess may exit the turbine system 10 via the diffuser 38 and theexhaust outlet 20. In some embodiments, the diffuser 38 may include acircumferential groove 40, one or more lap joints 42, one or morediscrete brackets 44, one or more poles 46 disposed between an aft plate62 and a forward plate 64 of the diffuser 38, or any combinationthereof. The rotating blades of the turbine 18 cause the rotation ofshaft the 28, which is coupled to several other components (e.g.,compressor 22, load 26) throughout the turbine system 10.

In an embodiment of the turbine system 10, compressor vanes or bladesare included as components of the compressor 22. Blades withincompressor the 22 may be coupled to the shaft 28 by a compressor rotor,and will rotate as the shaft 28 is driven by the turbine 18. Thecompressor 22 may intake oxidant (e.g., air) 30 to the turbine system 10via an air intake 24. Further, the shaft 28 may be coupled to the load26, which may be powered via rotation of the shaft 28. As appreciated,the load 26 may be any suitable device that may generate power via therotational output of the turbine system 10, such as a power generationplant or an external mechanical load. For example, the load 26 mayinclude an external mechanical load such as an electrical generator. Theair intake 24 draws the oxidant (e.g., air) 30 into the turbine system10 via a suitable mechanism, such as a cold air intake, for subsequentmixture of air 30 with fuel 14 via the fuel nozzle 12. The oxidant(e.g., air) 30 taken in by turbine system 10 may be fed and compressedinto pressurized air 32 by rotating blades within compressor 22. Thepressurized air 32 may then be fed into one or more fuel nozzles 12. Thefuel nozzles 12 may then mix the pressurized air 32 and fuel 14, toproduce a suitable air-fuel mixture 34 for combustion.

FIG. 2 illustrates a detailed diagram of the diffuser 38 section of theturbine 18. As depicted, the diffuser section 38 may include an upperportion 52 and a lower portion 54, which are shown as separated by aventilated bearing tunnel 56. The ventilated bearing tunnel 56 maysupply a cooling flow through the turbine outlet 20 and the diffusersection 38. It may be appreciated that the diffuser 38 has asubstantially annular shape that encloses a portion of the bearingtunnel 56. The upper portion 52 of the diffuser 38 is coupled to anexhaust frame 58 and is radially disposed within an exhaust plenum 60.The exhaust gases 36 exit through the upper and lower sections 52, 54 ofthe diffuser 38 into the exhaust plenum 60. The aft plate 62 of thediffuser section 38 is also disposed in the plenum 60. The inner barrel48 may be cooler than the outer barrel 50, particularly along portionsof the inner barrel 48 further away from the turbine outlet 20 in partdue to insulation applied to the inner barrel 48. As such, the aft plate62 may absorb heat more quickly than the inner barrel 48 contributing toa thermal gradient across the diffuser 38. This thermal gradient maycause stresses in the diffuser 38, thereby affecting the mechanicalintegrity of the diffuser 38.

The mechanical integrity of the diffuser 38 may also be affected bystresses related to the attenuation length from an air foil 82 disposedwithin the diffuser 38 and a vertical joint 74 of the exhaust frame 58.The flow path of the hot exhaust gases 36 may further reduce themechanical integrity of the diffuser 38 due to the vibratory forces andtemperature effects that may fatigue the diffuser 38. Accordingly,modifications to the diffuser 38 section as described in further detailin the discussion of FIG. 3 may reduce these effects on the diffuser 38.Such modifications may include manufacturing a desired curvature of thediffuser 38 section, disposing a plurality of the poles 46 between theforward plate 64 and the aft plate 62 of the diffuser 38, acircumferential groove 40 disposed in the inner barrel 48 to receive theaft plate 62, one or more circumferential lap joints 42, a plurality ofdiscrete brackets 44 disposed along the inner barrel 48 and the outerbarrel 50 of the diffuser 38 configured to couple the diffuser 38 to theexhaust frame 58, or any combination thereof. The circumferential lapjoint 42 and the discrete brackets 44 are configured to reduce movementin certain directions (e.g., circumferentially 66, axially 76,vertically 78, laterally 80) or facilitate movement (e.g.,circumferentially 66, axially 76, vertically 78, laterally 80, radially84), depending on how the circumferential lap joints 42 and the discretebrackets 44 are positioned.

FIG. 3 depicts the modified upper portion 52 of the diffuser 38 inaccordance with the present disclosure. The diffuser 38 section may bemanufactured such that the diffuser 38 begins to curve along the innerbarrel 48 and the outer barrel 50 of the diffuser 38 at the end nearestthe turbine outlet 20. The curvature 88 of the diffuser 38 may providestructural advantages over other diffuser shapes (e.g., more linearshaped diffusers). For example, the continuous curvature 88 of thediffuser 38 may reduce structurally-created stresses by improvingaerodynamic properties of the diffuser 38 as compared to approximating adesired curvature with linear plates. As discussed in detail below, thecurvature of the diffuser 38 may be formed by a suitable process, suchas a spinning process. In some embodiments, each of the inner barrel 48and the outer barrel 50 of the diffuser 38 is formed from more than onecone. The cone may be an annular sheet formed from a suitable material,as described with respect to FIG. 11. For example, the inner barrel 48may include 2, 3, or more cone-pieces. The outer barrel 50 may include2, 3, 4, 5, or more cone-pieces. The cone-pieces may then be subject tothe spinning process so that the desired curves of the cone-pieces areformed. The respective cone-pieces are then integrally coupled together(e.g., by welding) to form an integral diffuser 38 section, as describedfurther with respect to FIG. 11. Both the inner barrel 48 and the outerbarrel 50 cone-pieces may be formed by the spinning process. The innerbarrel 48 and the outer barrel 50 may be separate pieces which may becoupled together via the poles 46.

Other turbine modifications are disposed downstream 104 of the curvedportion of the diffuser 38. For example, the plurality of poles 46 maybe disposed circumferentially 66 between the forward plate 64 and theaft plate 62 of the diffuser 38. The poles 46 may be coupled to theforward plate 64 and the aft plate 62 to by a plurality of gussets 68 tosecure the poles 46 to the forward plate 64 and the aft plate 62. Thepoles 46 are disposed circumferentially 66 between the forward plate 64and the aft plate 62. The poles 46 may serve to reduce vibratorybehavior between the forward plate 64 and the aft plate 62. The poles 46may reduce the tendency of undesirable vibration by stiffening theforward plate 64 and the aft plate 62, thereby reducing resonance duringoperation of the gas turbine 18. The poles 46 may have varying diameters70 to accommodate flow of the exhaust gases 36. For example, the regionsin the diffuser outlet nearest the bottom, inner portion of the diffuseroutlet are equipped with poles 46 that have smaller diameters 70 tominimize blockage of the exhaust gases 36.

Also downstream 104 of the curved portion of the diffuser 38 is thecircumferential groove 40. The circumferential groove 40 is disposedwithin inner barrel 48. In some embodiments, the circumferential groove40 may be disposed on the inner barrel 48 to receive the aft plate 62.The circumferential groove 40 may reduce stresses (e.g., hoop stresses)in the region that may develop due to large temperature changes. Asdescribed above, the aft plate 62 is disposed within the exhaust plenum60 such that the aft plate 62 is exposed to approximately the sameoperating temperatures as the forward plate 64. The inner barrel 48 hubmay be insulated so that portions of the inner barrel 48 are exposed tocooler operating temperatures than the aft plate 62, thereby resultingin a large thermal gradient across the inner barrel 48 and the aft plate62. As such, the resulting thermal gradient may create stresses in theregion via thermal expansion of the inner barrel 48. The circumferentialgroove 40 may reduce stress by enabling a conical plate 72 of the aftplate 62 to move within the circumferential groove 40. By enablingslight movement in the radial direction 84 between the sections (e.g.,the conical plate 72 and the circumferential groove 40), the hoopstresses may be reduced in the region. As described in detail below, thestress reduction from implementing the circumferential groove 40 mayreduce hoop stresses by as much as one-half of the stresses experiencedby a traditional diffuser without the circumferential groove 40.

The placement of the lap joint 42 and discrete brackets 44 may bepartially defined by an attenuation length 100. The attenuation length100 is defined in part by a plurality of airfoils 82 disposed within theturbine outlet 20. The airfoil 82 is disposed between an outer wall 106of the turbine outlet 20 and an inner wall 112 of the turbine outlet 20proximate to a downstream 104 end of the turbine outlet 20. A shorterattenuation length 100 from an air foil 82 to the vertical joint 74 mayincrease stresses in the vertical joint 74, compared to otherconfigurations where the attenuation length 100 may be longer. Theattenuation length 100 may help define the location where thecircumferential lap joint 42 is disposed. For example, the lap joint 42may be disposed at a distance approximately equal to the attenuationlength 100 downstream of the air foils 82. In some embodiments, theattenuation length 100 is less than approximately 12 inches. Thediscrete brackets 44 may reduce movement of the diffuser 38 such thatmovement in the axial 76, vertical 78, and lateral 80 directions arerestricted depending on where the discrete brackets 44 are disposed onthe diffuser 38. As described in detail below, the discrete brackets 44disposed along the inner barrel 48 and the outer barrel 50 may beoriented differently to hold the aft plate 62 and the forward plate 64of the diffuser 38 in place.

Turning now to the inner barrel 48, the upstream end 102 of the innerbarrel 48 of the diffuser 38 section may be coupled to the downstreamend 104 of an inner wall 112 of the turbine outlet 20 by an innercircumferential joint 114. The inner circumferential joint 114 mayinclude the plurality of discrete brackets (e.g., brackets 47). Thediscrete brackets are configured to couple the downstream end 104 of theinner wall 112 of the turbine outlet 20 to the upstream end 102 of theinner barrel 48. The inner discrete brackets 47 are configured toaxially 76 support inner barrel 48.

On the inner barrel 48, a secondary flexible seal 101 (e.g., a secondcircumferential seal) may be disposed in an opening within a secondaryflex seal groove 102. The secondary flexible seal 101 may block hotexhaust gases 36 from entering the ventilated bearing tunnel 56. Thesecondary flexible seal 101 may include one or more plate segments whichare circumferentially segmented to make a 360 degree structure that maybe bolted at a first end 103. Similar to the flexible seal 92 of theouter barrel 50, the secondary flexible seal 101 may be uncoupledopposite the first end 103 so that the secondary flexible seal 101 maybe move freely within the opening of the secondary flex seal groove 102.

FIG. 4 depicts a cross-sectional view of the diffuser 38 taken throughthe brackets 44 along line 4-4 of FIG. 2. The curvature of the diffuser38 may begin after (e.g., downstream of) the portion of the diffuser 38where the lap joint 42 and discrete brackets 44 are disposed. Asdescribed above, the lap joint 42 and the discrete brackets 44 may bedisposed circumferentially 66 around the outer barrel 50 of the diffuser38. The discrete brackets 44 may be coupled to the outer barrel 50 and aframe assembly (e.g., exhaust frame 58). The discrete brackets 44 (e.g.,outer discrete brackets 45) are configured to support the outer barrel50 in the axial 76 direction and the circumferential direction 66.

Another set of the discrete brackets 44 may be disposedcircumferentially 66 within the inner barrel 48 of the diffuser 38. Forexample, a subset of the discrete brackets 44 may include a plurality ofsupport brackets (e.g., inner discrete brackets 47). The inner discretebrackets 47 may provide vertical 78 and/or lateral 80 support for theinner barrel 48 relative to the turbine outlet 20. Both the outerdiscrete brackets 45 and the inner discrete brackets 47 may be disposedabout the outer barrel 50 in a rotationally symmetric arrangement.

The inner barrel 48 is exposed to a cooling flow that flows through theventilated bearing tunnel 56. As such, the inner discrete brackets 47disposed within the inner barrel 48 may be made of materials thatmaintain yield strength at lower temperatures (e.g., compared to ahigher temperature of the outer barrel 50). The discrete brackets 44(e.g., the inner discrete brackets 47) may hold the diffuser (e.g.,inner barrel 48) in place and reduce movement in the axial direction 76and/or the lateral direction 80. The inner barrel 48 may include abolted joint at one end 49 to fix the diffuser 38 sections (e.g., theaft plate 62 of the diffuser and the forward plate 64 of the diffuser)to the turbine outlet 20. The discrete brackets 44 and supporting pairsof relaying blocks (see FIG. 6) enable thermal growth in the radialdirection 84.

The discrete brackets 44 may be coupled to the outer barrel 50 and theinner barrel 48 in various locations. In some embodiments, the discretebrackets 44 may be disposed at a 12 o'clock position 118, a 3 o'clockposition 120, a 6 o'clock position 122, a 9 o'clock position 124, or anycombination thereof. In some embodiments, discrete brackets 44 may bepositioned at other positions (e.g., 4 o'clock, 7 o'clock) such that theplacement of the discrete brackets 44 remains discrete (e.g., notcontinuous). Moreover, the position of the discrete brackets 44 may bearranged according to the desired restraint of the outer barrel 50 andthe inner barrel 48. In other words, the plurality of outer discretebrackets 45 and the plurality of inner discrete brackets 47 may becircumferentially 66 spaced about the turbine axis 76. The outerdiscrete brackets 45 are configured to position the outer barrel 50relative to the outer wall 106 of the turbine outlet 20 to form thecircumferential lap joint 42 between the outer wall 106 of the turbineoutlet 20 and the outer barrel 50 of the diffuser section 38. Thecircumferential lap joint 42 is continuous. The movement of the diffuser38 (e.g., the inner barrel 48 and the outer barrel 50) relative to theturbine outlet 20 may be reduced and/or restrained depending on wherethe lap joint 42 and discrete bracket 44 are disposed along the outerbarrel 50. For example, when the discrete bracket 44 are disposed at the3 o'clock position 120 and/or the 9 o'clock position 124, the diffuser38 (e.g., the inner barrel 48 and the outer barrel 50) is restrained inthe axial direction 76 and in the vertical direction 78. When thediscrete bracket 44 are disposed at the 12 o'clock position 118 and/orthe 6 o'clock position 122, the diffuser 38 (e.g., the inner barrel 48and the outer barrel 50) is restrained in the axial direction 76 and inthe lateral direction 80. The discrete brackets 44 may be supported bysupport components (e.g., a pin) as described further in FIG. 6. Thesupport components may restrict movement in the circumferentialdirection 66.

FIG. 5 depicts a perspective view of the lap joint 42 and the discretebracket 44, along line 5-5 of FIG. 4. As described above, the discretebrackets 44 may be coupled to the outer barrel 50 and the frame assembly58 (e.g., diffuser frame 116). The discrete brackets 44 are configuredto support the outer barrel 50 in the axial 76 direction, and at leastsome of the discrete brackets 44 support the outer barrel in thecircumferential direction 66.

The circumferential lap joint 42 is disposed between the downstream end104 of the outer wall 106 of the turbine outlet 20 and the upstream end102 of the outer barrel 50 of the diffuser 38 section. Thecircumferential lap joint 42 is configured to facilitate axial 76movement of the outer barrel 50 relative to the outer wall 106 of theturbine outlet 20, thereby relieving stress in the outer barrel 50. Anupstream lip (e.g., outer lip 96) of the outer barrel 50 is disposedradially 84 within a downstream lip (e.g., lip 128) of the outer wall106 to facilitate ease of movement of the lap joint 42. The stressreduction by use of the upstream lip and the downstream lip is furtherincreased by the use of discrete brackets 44. The outer discretebrackets 45 limit the heat transfer from the exhaust frame 58 to theouter barrel 50. Thus, thermal expansion and contraction is likely tooccur at fewer places than with a continuous bracket interface, and thethermal stress is controlled to be primary at the brackets 45. Forexample, the diffuser 38 section may include the plurality of discretebrackets 44 disposed along the outer barrel 50 (e.g., outer discretebrackets 45) of the diffuser 38 to reduce stress in the vertical joint74 of the exhaust frame 58.

In some embodiments, a flexible seal 92 may be utilized in the lap joint42 and discrete bracket 44 assembly. The flexible seal 92 may bedisposed proximate to the upstream lip 96 of the outer barrel 50. Theflexible seal 92 may be positioned between insulation 126 disposedaround the discrete bracket 44 and a flex seal groove 94 of the outerwall 106 of the turbine outlet 20. The flexible seal 92 may include oneor more plate segments which are circumferentially segmented to make a360 degree structure that may be bolted or fastened at a first end 93.The flexible seal 92 may remain uncoupled (e.g., unbolted) opposite thefirst end 93 so that the flexible seal 92 may move freely within theflex seal groove 94 to seal a clearance space 95 between the flexibleseal 92 and an end opposite the bolted end (e.g., first end 93 offlexible seal 92). The flexible seal 92 may discourage a cooling flowfrom along an outer surface of the turbine outlet 20 (e.g., forclearance control) into the diffuser 38. A slot 98 between the outerwall 106 of the turbine outlet 20 and the outer lip 96 of the outerbarrel 50 may facilitate some axial 76 movement of the lap joint 42. Thelip 96 may radially 84 interface with the outer lip 128 of the lap joint42.

As described above, the hot exhaust gases 36 that flow through theturbine 18 and diffuser 38 are received in the exhaust plenum 60. Theflexible seal 92 may insulate a cooling flow (e.g., in the exhaustframe) from the hot exhaust gases 36 downstream 104 of the flexible seal92. A primary flow path may 130 extend from the turbine outlet 20 to adiffuser outlet of the diffuser 38 section through an interior region134 of the diffuser 38. The interior region 134 is radially 84 withinthe outer wall 106 and the outer barrel 50 between the outer barrel 50and the inner barrel 48. The diffuser outlet is configured to direct theexhaust flow 36 to the exhaust plenum 60. A secondary flow path 136 mayextend from the exhaust plenum 60 to the interior region 134 through theslot 98 between the downstream lip 128 of the outer wall 106 and theupstream lip 96 of the outer barrel 50. The secondary flow path 136 mayextend through the circumferential lap joint 42. In some embodiments,the secondary flow path 136 may include a non-zero portion of theexhaust flow 36 of the interior region 134.

FIG. 6 depicts a perspective view of the lap joint 42 and the discretebracket 44, along line 5-5 of FIG. 4. In some embodiments, the discretebrackets 44 may be supported by a pin 86 extending axially 76 through aflange 116 of the outer barrel 50, a flange 116, and a pair of relayingblocks 90. The pin 86 may be disposed through the flange 116 and therelaying blocks 90 to support the discrete bracket 44. The pin 86 isconfigured to enable movement (e.g., via sliding) in the radialdirection 84 of the outer barrel 50 relative to the respective bracket44. As described above, the plurality of outer discrete brackets 45includes the plurality of circumferential support brackets 44 (e.g., asubset of the plurality of discrete brackets). Each support bracket 44of the plurality of discrete outer brackets 45 utilizes the pin 86 toenable movement in the radial direction 84 of the outer barrel 50relative to the respective support bracket 45. The relaying blocks 90and the support bracket 47 restrict movement in the circumferentialdirection 66.

Similar to the discrete outer brackets 44, the plurality of innerdiscrete brackets 47 may include a plurality of inner circumferentialsupport brackets that each utilize a respective pin 86 to extend axially76 through respective flanges of the inner wall 112 and the inner barrel48. The pins 86 are configured to enable radial 84 movement of the innerbarrel 48 relative to the respective inner support bracket whilerestricting circumferential 66 movement.

FIG. 7 depicts an axial cross-sectional view of the circumferentialgroove 40 within the inner barrel 48 of the diffuser 38 of FIGS. 2 and3. The aft plate 62 interfaces with the inner barrel 48 of the diffuser38 at the circumferential groove 40. As described above, the innerbarrel 48 and the outer barrel 50 are disposed about the turbine axis76. The aft plate 62 is disposed at least partially within the exhaustplenum 60 and is disposed downstream 104 of the inner barrel 48.

The circumferential groove 40 may reduce stresses (e.g., hoop stresses)in the region that may form due to large thermal gradients. The aftplate 62 and the forward plate 64 are disposed at least partially withinthe exhaust plenum 60. The hub of the inner barrel 48 is insulated suchthat the inner barrel 48 hub is exposed to cooler operating temperaturesthan the aft plate 62, thereby resulting in different temperatures atthe aft plate 62 and the inner barrel 48 hub. The difference intemperatures between the aft plate 62 and the inner barrel 48 hubresults in a large thermal gradient across the hub of the inner barrel48 and the aft plate 62. The resulting thermal gradient creates stressesin the region due to thermal expansion/contraction. The hoop stressesmay be reduced in the region by enabling slight movement (i.e., upstreammovement, downstream movement) between the sections (e.g., the conicalplate 72 and the circumferential groove 40). The stress reduction fromimplementing the circumferential groove 40 may reduce hoop stresses byas much as one-half. For example, the stresses in the aft plate 62region may be reduced from approximately 413 MPa when thecircumferential groove 40 is not present in the inner barrel 48 to about207 MPa when the circumferential groove 40 is present in the innerbarrel 48.

A seal interface 140 disposed at a downstream 104 end of the innerbarrel 48 and the aft plate 62 includes the circumferential groove 40.In some embodiments, the seal interface 140 is mechanically coupled(e.g., welded, fused, brazed, bolted, fastened) to the downstream end104 of the inner barrel 48. In some embodiments, the seal interface 140is formed at the downstream end of the inner barrel 48. The sealinterface 140 may include a first circumferential groove 142 and asecond circumferential groove 144. The first circumferential groove 142is configured to receive the aft plate 62. As such, the firstcircumferential groove 142 opens in a first direction 146 (e.g.,downstream 104) away from the turbine axis 76. The secondary flexibleseal 101 is configured to isolate the exhaust plenum 60 from theventilated bearing tunnel 56. The second circumferential groove 144opens in a second direction 150 (e.g., upstream) towards the turbineaxis 76.

The first circumferential groove 142 and the second circumferentialgroove 144 enable some upstream and downstream movement of the innerbarrel 48 relative to the aft plate 62, resulting in reduced stresses inthe region. In the illustrated embodiment, the aft plate 62 isconfigured to interface with a root 160 of the first circumferentialgroove 142 at the 12 o'clock position 118 of the seal interface 140. Theseal interface 140 reduces space between the first circumferentialgroove 142 and the root 160 so that no gap at the 12 o'clock position118 is formed. The seal interface 140 also contributes to stressreduction in the poles 46 by enabling the seal interface of the innerbarrel 48 to support some of the vertical load of the aft plate 62. Theaft plate 62 may be offset from the root 160 of the firstcircumferential groove 142 at the 6 o'clock position 122 (e.g., oppositeof the 12 o'clock position 118) of the seal interface 140.

The aft plate 62 may be made up of a plurality of circumferentialsegments 152 (e.g., aft plate segments, conical plate 72). In someembodiments, one or more of the plurality of circumferential segments152 may include a stress relieving feature 154 disposed along a joint156 between the circumferential segments 152 of the aft plate 62, asdescribed with respect to FIG. 10. The stress relieving features 154 maybe concentrated towards an end portion of the circumferential segments152 (e.g., aft plate segments) proximate to the seal interface 140.

In one embodiment, the aft plate 62 includes an aft plate assembly 65,which may be made up of a plurality of aft plate segments 67 (see FIG.8). The aft plate assembly 65 may include 2, 3, 4, 5, 6, or more aftplate segments 67. It may be appreciated that reducing the number of aftplate segments 67 contributes to reducing the assembly time in theregion by reducing the components associated with the aft plate assembly65. The aft plate assembly 65 may be an annular aft plate assembly thatextends circumferentially 66 about an axis 76 of the inner barrel. Thecircumferential groove 40 also extends circumferentially 66 about theaxis 76 of the inner barrel. The aft plate segments 67 may be joinedtogether in a suitable manner, such as by welding, brazing, fusing,fastening, or any combination thereof. In the illustrated embodiment,the aft plate assembly 65 reduces space between the firstcircumferential groove 142 and the root 160 so that no gap at the 12o'clock position 118 is formed. As described further with reference toFIGS. 8 and 9, the aft plate segments 67 may include a plurality ofnotches 71 and a plurality of ridges 73. The plurality of ridges 73 maybe disposed on a radially interior surface 75 of the aft plate 62. Thenotches 71 and ridges 73 may allow a reduction in thermal mass of theaft plate assembly 65. Reducing the thermal mass of the aft plateassembly 65 may contribute to reduced thermal stresses in the regionand/or more uniform heat transfer among components of the aft plateassembly 65 when the turbine is operating.

FIG. 8 depicts an axial view of an embodiment of the aft plate assembly65 taken along line 8-8 of the diffuser 38 of FIG. 7. In the illustratedembodiment, the aft plate assembly 65 includes three aft plate segments67. As described above, the aft plate assembly 65 may include any numberof aft plate segments 67, including 2, 3, 4, 5, 6, or more aft platesegments 67 to form a 360 degree structure (e.g., annular aft plateassembly). The segments 67 may be joined together by any suitablejoining process, such as welding or fusing along joints 156. In someembodiments, each aft plate segment 67 may include one or more notches71 (e.g., a receiving portion) and one or more ridge 73 (e.g., aninserted portion). The notches 71 and the ridges 73 are disposed on aradially interior surface 75 of the aft plate 62. The aft plate assembly65 includes a downstream lip 61 of the inner barrel 48. The downstreamlip 61 of the aft plate assembly 65 has a plurality of notches 79 and aplurality of ridges 83. In the illustrated embodiment, the radiallyinterior surface 75 of the aft plate 62 may be inserted axially 76 intothe circumferential groove 40 such that the ridges 73 of the aft plate62 pass axially through the notches 79 of the downstream lip 61, and theridges 83 of the downstream lip 61 pass axially through the notches 71of the interior surface 75 of the aft plate 62. Inserting the aft plate62 into the circumferential groove 40 may include inserting a firstridge 81 of the aft plate 62 into a first notch 85 of the inner barrel48. When the first ridge 81 is inserted into the first notch 85, the aftplate 62 is disposed in a first circumferential orientation 87 (e.g., afirst position) relative to the inner barrel 48. That is, the aft plateassembly 65 is in the first circumferential orientation 87. The aftplate 62 may be turned (e.g., rotated in a circumferential direction 66)to a second circumferential orientation 89 (e.g., a second position)such that the first ridge 81 axially overlaps with a second ridge 111 ofthe downstream lip 61.

The aft plate 62 of the aft plate assembly 65 may be turned or rotatedapproximately 15 to 60 degrees, 30 to 45 degrees, 35 to 40 degrees, orany subranges therebetween. When the aft plate 62 is turned, indicatedby arrow 69, to the second circumferential orientation 89 relative tothe inner barrel 48, the aft plate assembly 65 is configured to retainthe aft plate 62 axially 76 in the circumferential groove 40. The firstcircumferential orientation 87 is circumferentially offset about theaxis 76 of the inner barrel 48 from the second circumferentialorientation 89 by less than approximately 60 degrees. In someembodiments, the first circumferential orientation 87 iscircumferentially offset about the axis of the inner barrel 76 from thesecond circumferential orientation 89 by less than approximately 30degrees. A method of forming the aft plate assembly 65 by inserting theplurality of ridges 73 of the aft plate 62 through the plurality ofnotches 71 of the downstream lip 61 may be further understood withreference to FIG. 12. It may be appreciated that the aft plate assembly65 may enable leakage of the exhaust gases through the connectionbetween the aft plate 62 and the inner barrel 48. The leakage of exhaustgases through the aft plate assembly 65 may reduce stresses on the aftplate 62, the inner barrel 48, or some combination thereof. The leakagemay be reduced when the ridges 73 are turned to the secondcircumferential orientation 89 such that the ridges 73 of the aft plate62 axially overlap with the ridges 83 of the inner barrel 48. In oneembodiment, the leakage of the exhaust gases may be 0.01 to 3 percent,0.05 to 2 percent, 1 to 1.5 percent of the exhaust flow gases, or anysubranges therebetween.

FIG. 9 depicts a partial cross-sectional view of the aft plate assembly.As illustrated and as describe above, the aft plate assembly 65 includesthe plurality of apertures 176 to receive the plurality of poles 46. Oneor more apertures 176 may be disposed in the aft plate segments 67. Theaft plate segments 67 may be joined together via fusing, brazing,welding, or any other suitable process. The aft plate segments 67 mayform joints 156 (e.g., a welded joint, a brazed joint, a fused joint, afastened joint) where the aft plate segments 67 are joined together. Asillustrated, the aft plate segment 67 includes a radial ridge height 91between a root 97 of a respective notch 71 and a crest 99 of theadjacent ridge 73. Additionally, the downstream lip 61 of the innerbarrel 48 may have substantially the same or greater radial ridge height91 between the root 97 of a respective notch 79 and the crest 99 of theadjacent ridge 83. In one embodiment, the radial height 91 is less thana radial height 105 of the upstream lip 77 of the circumferential groove40.

FIG. 10 depicts an axial view an embodiment of the aft plate 62 of theinner barrel 48 taken along line 8-8 of the diffuser 38 of FIG. 7. Inthe illustrated embodiment, the downstream end 104 of the aft plate 62coupled to the downstream end 104 of the forward plate 64 via theplurality of poles 46. As described above, the inner barrel 48 and theouter barrel 50 are disposed around the turbine axis 76. As such, theplurality of poles 46 may be circumferentially 66 spaced about theturbine axis 76.

As described above, the aft plate 62 may be made up of the plurality ofcircumferential segments 152 (e.g., aft plate segments, conical plate72). The plurality of circumferential segments 152 may include theplurality of stress relieving features 154 disposed along the pluralityof joints 156 between the circumferential segments 152 of the aft plate62. The plurality of stress relieving features 154 may be any suitableshape to accomplish the stress relief including circular, heart-shaped,bean-shaped, or any combination thereof.

In some embodiments, the poles 46 have varying pole diameters 70. Thepole diameter 70 is based in part on the circumferential 66 location ofthe pole 46 location along the diffuser 38. For example, the diameter 70of the poles 46 nearest a top portion 172 of the aft plate 62 and theforward plate 64 have a larger diameter 70 than the poles 46 nearest abottom portion 174 of the aft plate 62 and the forward plate 64.Accordingly, a plurality of apertures 176 correspond to the plurality ofpoles 46 disposed within the diffuser 38. The apertures 176 may varybased in part on the circumferential 66 location of the apertures 176 tocouple to outer aft plate 62 and the inner aft plate 63 via theplurality of poles.

In the illustrated embodiment, a first set 178 (see FIG. 2) of poles 46disposed at circumferential 66 locations within the bottom portion 174of the diffuser 38 section may have a non-uniform axial cross-section.For example, the first set 178 of poles 46 may have an ovular,elliptical, spherical, or other non-uniform portion of the axialcross-section. The non-uniform portion of the poles 46 within the bottomportion 174 of the diffuser 38 section may enable the poles 46 toexhibit more elasticity (e.g., in the radial direction 84) than circularpoles 46, which may reduce stresses in the bottom portion 174. In someembodiments, the poles diameters 70 are smaller to reduce aerodynamiceffects on the flow of the exhaust gases 36. As such, smaller polediameters 70 may be beneficial by reducing blockage of the exhaust flowpath 36.

FIG. 11 depicts an axial view of an embodiment of the aft plate assembly65 of the inner barrel 48 taken along line 8-8 of the diffuser 38 ofFIG. 7. As described above, the aft plate assembly 65 includes aplurality of aft plate segments 67. The aft plate assembly 65illustrated in FIG. 11 is in the second circumferential orientation 89such that the ridges 73 of the aft plate 62 are axially retained by theridges 83 of the downstream lip 61 of the inner barrel 48, as describedabove. The aft plate segments 67 include apertures 176 to receive thepoles 46 to couple the downstream end 104 of the aft plate 62 to thedownstream end 104 of the forward plate 64. The poles 46 may be coupledto the aft plate segments 67 as described above with reference to FIG.10. That is, the first set 178 (see FIG. 2) of poles 46 disposed atcircumferential locations within the bottom portion 174 of the diffuser38 section may have a non-uniform axial cross-section. In theillustrated embodiment, the aft plate segments 67 do not include thestress relieving features 154 as shown in the aft plate 62 describedwith reference to FIG. 10 above.

FIG. 12 describes a method of forming the aft plate assembly 65according to an embodiment of the present disclosure. The aft plateassembly 65 may be formed by a method 190. The method 190 may includejoining (block 192) the plurality of aft plate segments 67 in the radialdirection 84 to each other by welding, fusing, brazing, bolting, orfastening, or any combination thereof. The joined aft plate segments 67form the aft plate 62. The method 190 may include interfacing (block194) the aft plate 62 with the 160 root of the first seal interface 162the 12 o'clock position 118. As described above, the aft plate 62 may beinserted axially through the downstream lip 61 of the inner barrel 48via complementary notches and ridges so that the aft plate 62 isdisposed within the circumferential groove of the inner barrel 48. Thatis, in a first circumferential position 87, ridges 73 of the aft plate62 may be inserted axially through notches 79 of the downstream lip 61,and notches 71 of the aft plate 62 may axially receive ridges 83 of thedownstream lip 61. In some embodiments, the 6 o'clock position 122 ofthe aft plate 62 is offset (e.g., spaced apart radially) from the root160. The method 190 may include rotating (block 196) the aft plate 62about the axis of the inner barrel 48. As described above, the aft plateassembly 65 may be rotated from the first circumferential position 87 toa second circumferential position 89. In some embodiments, the aft plate62 is rotated approximately 15 to 45 degrees relative to the innerbarrel 48. The method 190 may further include attaching (block 198) thepoles 46 between the downstream end 104 of the aft plate 62 coupled tothe downstream end 104 of the forward plate 64 via the plurality ofpoles 46.

Returning now to FIG. 10, the poles 46 disposed within the top portion172 of the diffuser 38 may be configured to support the load (e.g.,weight) of the diffuser 38. For example, the poles 46 disposed withinthe top portion 172 of the diffuser 38 may be utilized to lift thediffuser 38. In some embodiments, the poles 46 disposed within the topportion 172 of the diffuser 38 section may be coupled to a hoist, lift,crane, or other suitable lifting machine to move the assembled diffuser38 with aft plates 62 to a suitable location (e.g., move forinstallation, removal, service, repair).

Each of the plurality of poles 46 includes a pole axis. In someembodiments, the plurality of poles 46 may be substantially parallel toa common pole axis (e.g., the turbine axis 76). It should be appreciatedthe plurality of poles 46 do not support a plurality of turning vanes.Moreover, in some embodiments, no turning vanes are disposed in thediffuser 38. Poles are positioned at or near the downstream end of thediffuser 38 to reduce vibration and to facilitate installation.

FIGS. 13 and 14 depict a side view of the inner barrel 48 and the outerbarrel 50 of the diffuser 38. As illustrated within the solid lines, theinner barrel 48 and the outer barrel 50 are curved to reduce stresses inthe diffuser 38. The curvature 88 of the inner barrel 48 and the outerbarrel 50 begins downstream of the turbine section 18. Portions of theinner barrel 48 and the outer barrel 50 are disposed within the exhaustplenum 60. FIG. 13 depicts a side view of an embodiment of the outerbarrel 50. The outer barrel 50 includes a first plurality of axialsegments 180 disposed downstream of the outer barrel 50. In theillustrated embodiment, the outer barrel 50 includes two segments (e.g.,axial segments). Though two axial segments are shown, it will beappreciated that the outer barrel may include three, four, or more axialsegments. The first plurality of outer barrel segments 180 are joinedtogether in the axial direction and form an outer barrel interface 188between each of the outer barrel segments 180. As described above,joining may include welding, brazing, fusing, fastening, or anycombination thereof. The first plurality of outer barrel segments 180includes a first continuous curve 182 that curves away from the turbineaxis 76 (e.g., from the upstream end of the outer barrel 50 to the outeraft plate 62).

FIG. 14 depicts a side view of the inner barrel 48. In the illustratedembodiment, the inner barrel 48 includes four segments (e.g., axialsegments). The inner barrel 48 includes a second plurality of axialsegments 184 disposed between the upstream end of the inner barrel 48and the seal interface 140. Though four axial segments are shown, itwill be appreciated that the inner barrel 48 may include three, four,five, six, or more axial segments 184. The second plurality of axialsegments 184 are joined together in the axial direction and form aninner barrel interface 208 between each of the inner barrel segments184. As described above, joining may include welding, brazing, fusing,fastening, or any combination thereof. The second plurality of axialsegments 184 (e.g., inner barrel segments) includes a second continuouscurve 186 that curves away from the turbine axis 76 (e.g., from theupstream end of the inner barrel 48 to the seal interface 140). As willbe appreciated, the second plurality of axial segments 184 (e.g., of theinner barrel 48) is greater than the first plurality of axial segmentsof the outer barrel 50 due to the arrangement of the inner barrel 48 andthe outer barrel 50. The curvature of the both the inner barrel 48 andthe outer barrel 50 may be further understood with respect to thediscussion of the spinning process, as described in FIG. 15.

FIG. 15 illustrates exemplary equipment used to machine the inner barrel48 and the outer barrel 50 into the desired continuous curvature, asdescribed in FIGS. 13-14. The first and the second continuous curves182, 186 (e.g., of the outer barrel, of the inner barrel) may be createdvia a suitable cold machining process, such as a spinning process. Thespinning process involves molding a suitable material 204 (e.g.,stainless steel) for the inner barrel 48 and the outer barrel 50 intothe desired shape by placing the material over a mold 206. The material204 is then molded into the desired shape by utilizing a roller 202 topress the material into the mold 206, thereby gradually forming thedesired mold shape.

The spinning process described above enables the desired curvature ofdiffuser 38 to provide required turbine engine performance (e.g.,through reduced stresses). To reduce residual stresses encountered viathe spinning process, the inner and outer barrels 48, 50 may be formedfrom multiple axial segments (e.g., first plurality of axial segments180, second plurality of axial segments 184). Utilizing more axialsegments to create the inner barrel 48 and the outer barrel 50 mayrequire less deformation of each segment to create the desired shape ofthe inner barrel 48 and the outer barrel 50, thereby reducing the amountof residual stresses that remain in the completed diffuser 38.

Once the axial segments (e.g., first plurality of axial segments 180,second plurality of axial segments 184) are formed, the axial segmentsmay be joined together. The axial segments may be cut from the suitablematerial to ensure the axial segments (e.g., first plurality of axialsegments 180, second plurality of axial segments 184) have excessmaterial so that the segments can be adequately joined together. Theaxial segments may be axially joined together by welding, brazing,fusing, bolting, fastening, or any combination thereof.

FIG. 16 illustrates a method 300 of forming the inner barrel 48 and theouter barrel 50 by the spinning process. The spinning process, asdescribed herein, may utilize a roller to spin about an axis of a moldor the mold may spin about the axis under the roller. As describedabove, the method 300 includes forming (block 302) a first plurality ofaxial forward plate segments of an outer barrel 50 by spinning asuitable material on the mold. As described above, the spinning processfor each segment involves molding a suitable material (e.g., stainlesssteel, metal) into the desired shape by placing the material over amold. The material is then molded into the desired shape by utilizing aroller to press the material into the mold, thereby gradually deformingthe material the desired mold shape. The method 300 also includesforming (block 304) a second plurality of axial aft plate segments of aninner barrel 48 by spinning a suitable material on a mold. After theaxial segments are formed, the method 300 includes joining (block 306)the first plurality of axial forward plate segments to one another toform the outer barrel 50 and joining (block 308) the second plurality ofaxial aft plate segments to one another to form the inner barrel 48.Both the inner barrel 48 and the outer barrel 50 are coupled to the gasturbine engine 18. As described above with respect to FIG. 7, acircumferential groove may be machined into the inner barrel 48.

Technical effects of the invention include improving traditionaldiffusers through utilization of mechanical improvements on the diffusersection. The mechanical improvements to the diffuser include an aftplate assembly with notches and ridges to facilitate axial installationof the aft plate to an inner barrel. The aft plate may be insertedaxially through notches of a circumferential groove of the inner barrelof the diffuser section, then rotated circumferentially within thecircumferential groove such that ridges axially retain the aft plateassembly. The mechanical improvements to the diffuser contribute toimproved mechanical integrity of the diffuser by reducing stressesassociated with a traditional diffuser design. The embodiments of themechanical improvements include manufacturing a desired curvature of thediffuser, disposing a plurality of poles between a forward plate and theaft plate of the diffuser, a circumferential groove disposed in theinner barrel to receive the aft plate, a circumferential lap joint, aplurality of discrete brackets disposed along the inner barrel and theouter barrel of the diffuser configured to couple the diffuser to theturbine outlet, or any combination thereof.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

1. A method comprising: inserting axially a radially interior surface ofan aft plate assembly into a circumferential groove of an inner barrelof a diffuser section of a gas turbine, wherein the aft plate assemblyis inserted into a first circumferential orientation relative to thecircumferential groove, and the circumferential groove is disposed on aradially exterior surface of the inner barrel; rotating the aft plateassembly circumferentially within the circumferential groove from thefirst circumferential orientation to a second circumferentialorientation, wherein the inner barrel is configured to axially retainthe aft plate assembly when the aft plate assembly is disposed in thesecond circumferential orientation.
 2. The method of claim 1, whereinthe aft plate assembly comprises an annular aft plate assembly extendingcircumferentially about an axis of the inner barrel, and thecircumferential groove extends circumferentially about the axis.
 3. Themethod of claim 1, wherein the aft plate assembly comprises a pluralityof aft plate segments.
 4. The method of claim 3, comprising joining theplurality of aft plate segments together, wherein joining compriseswelding, brazing, fusing, fastening, or any combination thereof.
 5. Themethod of claim 1, wherein the aft plate assembly comprises a firstplurality of notches and a first plurality of ridges on the radiallyinterior surface, the circumferential groove comprises a downstream lip,and the downstream lip comprises a second plurality of notches and asecond plurality of ridges.
 6. The method of claim 5, wherein insertingaxially the radially interior surface of the aft plate assembly into thecircumferential groove of the inner barrel comprises inserting the firstplurality of ridges through the second plurality of notches, and thesecond plurality of notches is configured to axially retain the firstplurality of notches when the aft plate assembly is disposed in thesecond circumferential orientation.
 7. The method of claim 5, wherein aradial ridge height between a root of a respective notch of the firstplurality of notches and a crest of an adjacent respective ridge of thefirst plurality of ridges is less than a radial height of an upstreamlip of the circumferential groove, wherein the first plurality of ridgesare disposed between the upstream lip and the second plurality of ridgeswhen the aft plate assembly is disposed in the second circumferentialorientation.
 8. The method of claim 1, comprising coupling a pluralityof poles between the aft plate assembly and a forward plate of thediffuser section.
 9. The method of claim 1, wherein the firstcircumferential orientation is circumferentially offset about an axis ofthe inner barrel from the second circumferential orientation by lessthan approximately 30 degrees.
 10. A system comprising: a diffusersection configured to receive an exhaust gas from a turbine section,wherein the diffuser section comprises: an aft plate assembly comprisinga radially interior surface, wherein the radially interior surfacecomprises a first notch and a first ridge; and an inner barrelcomprising a circumferential groove disposed on a radially exteriorsurface, wherein the circumferential groove comprises: an upstream lip;and a downstream lip comprising a second notch and a second ridge,wherein the first ridge is configured to be disposed in thecircumferential groove when the aft plate assembly is disposed in afirst circumferential orientation and a second circumferentialorientation relative to the inner barrel, the first ridge is axiallyaligned with the second notch in the first circumferential orientation,and the first ridge is circumferentially offset from the second notch inthe second circumferential orientation.
 11. The system of claim 10,wherein the aft plate assembly comprises a plurality of aft platesegments.
 12. The system of claim 11, wherein the plurality of aft platesegments are joined together to form an annular aft plate assembly, andthe plurality of aft plate segments are joined together by at least oneof a welded joint, a brazed joint, a fused joint, and a fastened joint,or any combination thereof.
 13. The system of claim 10, wherein theradially interior surface comprises a first plurality of notches and afirst plurality of ridges, the radially exterior surface comprises asecond plurality of notches and a second plurality of ridges, whereinthe first plurality of ridges is axially aligned with the secondplurality of notches in the first circumferential orientation, and thefirst plurality of ridges is axially aligned with the second pluralityof ridges in the second circumferential orientation.
 14. The system ofclaim 10, wherein a radial ridge height between a root of the firstnotch and a crest of the first ridge is less than a radial height of theupstream lip of the circumferential groove.
 15. The system of claim 10,wherein the diffuser section comprises: a forward plate; and a pluralityof poles coupled to the forward plate and the aft plate assembly whenthe aft plate assembly is disposed in the second circumferentialorientation.
 16. The system of claim 10, wherein the firstcircumferential orientation is circumferentially offset from the secondcircumferential orientation by less than approximately 30 degrees.
 17. Asystem comprising: a diffuser section configured to receive an exhaustgas from a turbine section, wherein the diffuser section comprises: aforward plate; an aft plate assembly comprising a radially interiorsurface, wherein the radially interior surface comprises a firstplurality of notches and a first plurality of ridges; and an innerbarrel comprising a circumferential groove disposed on a radiallyexterior surface, wherein the circumferential groove comprises: anupstream lip; and a downstream lip comprising a second plurality ofnotches and a second plurality of ridges, and a plurality of polescoupled between the forward plate and the aft plate assembly when theaft plate assembly is disposed in a second circumferential configurationrelative to the inner barrel; wherein the first plurality of ridges isconfigured to be disposed in the circumferential groove when the aftplate assembly is disposed in a first circumferential orientation andthe second circumferential orientation relative to the inner barrel, thefirst plurality of ridges is axially aligned with the second pluralityof notches in the first circumferential orientation, and the firstplurality of ridges is circumferentially offset from the secondplurality of notches in the second circumferential orientation.
 18. Thesystem of claim 17, wherein the aft plate assembly comprises a pluralityof aft plate segments joined together to form an annular aft plateassembly, and the plurality of aft plate segments are joined together byat least one of a welded joint, a brazed joint, a fused joint, and afastened joint, or any combination thereof.
 19. The system of claim 17,wherein a crest of a first ridge of the first plurality of ridges isconfigured to interface with a root of the circumferential groove at a12 o'clock position when the aft plate assembly is disposed in thesecond circumferential orientation relative to the inner barrel.
 20. Thesystem of claim 17, wherein each pole of the plurality of polescomprises a diameter, and the diameter of each pole is based at least inpart on a circumferential location of the respective pole about an axisof the diffuser section.